Resource utilization of waste solar photovoltaic panels for preparation of microporous silicon nanoparticles

Abstract

With the exponential growth of global photovoltaic (PV) installed capacity, the quantity of discarded PV modules continues to rise. This study innovatively explored the sustainable recovery and utilization of raw materials from discarded solar panels, focusing on the transformation of recycled silicon into microporous silica nanoparticles (MSN). Low toxic organic solvent ethyl acetate (EA) was for the first time utilized to reduce the viscosity of ethylene–vinyl acetate (EVA) and facilitated its removal. A simple combination of nitric acid (HNO₃) and sodium hydroxide (NaOH) at low temperatures (225 min HNO₃ etching at room temperature followed by 40 min NaOH etching at 70 °C) completely removed the deep blue anti-reflective coating SiN_x and successfully removed metallic impurities such as silver (Ag), aluminum (Al). Removal efficiencies for Ag and Al electrodes both reached 99 %, with recovery rates of 92 % and 99 % for Ag and Al, respectively. The recycled Ag and Si had a purity of 99 % and 93.2 %, respectively. The recycled pure Si was then dissolved in a NaOH solution to prepare a sodium silicate (Na₂SiO₃) solution. Under acidic conditions, the non-ionic surfactant Triton X-100 and cationic surfactant cetyltrimethylammonium bromide (CTAB) were used to transform the Na₂SiO₃ solution to the MSN. The specific surface area of the MSN measured by BET was 855.30 m²/g, with a pore size of 1.85 nm and a pore volume of 0.3963 cm³/g. This study highlights the innovative utilization of recovered silicon to fabricate advanced microporous materials, paving the way for high-value applications and promoting a sustainable photovoltaic industry.